1. Field of the Invention
In a system comprising two elements which are movable relatively to each other, at least one can be positioned along a predetermined direction relatively to the other, or both elements may be displaced along predetermined directions to be positioned relatively to each other a device is needed which provides for the displacements with a certain precision e.g. for a coarse and a fine positioning. As an example, in information storage and retrieval systems using a tape as an information storage medium, and a writing and/or reading head to store and/or retrieve the information from the tape it may be critical to precisely position the tape and the writing and/or reading head relatively to each other. More particularly in the case of magnetic tapes the information is usually stored in at least one longitudinal track on the tape. An active part of the magnetic head used to write and/or read a track, or any other device, e.g. a magneto-optic system to read a track, is coarse positioned on a track and fine positioned on the transverse center of the same track while the tape is being longitudinally transported. This problem has often been encountered in prior art and different solutions have been elaborated.
2. Discussion of Background
In a device shown in the U.S. Pat. No. 5,379,170 a recording/playback head is moved relatively to a magnetic tape in order to remain on the center of a track. The device comprises mechanisms which allow to perform a coarse and fine transverse head positioning. A stage actuated by a stepper motor driven lead screw provides for the coarse positioning. A pivotal arm mounted on the stage and actuated by a coil assembly provides a fine position control. The fine and coarse positioning mechanisms are clearly of distinct nature and use different actuators. The mechanical complexity of this prior art device is relatively high.
It is an object of the present invention to propose a solution for a single mechanism which allows to coarse and fine position a first element and a second element relatively to each other but which is more simple than in prior art.